Based on the communicating vessel principle, we present a new instrument for the measurement of bearing elevation change. A number of cups are attached to the bearings. They are linked with pipes and joints together to constitute a measurement network. Special features of the instrument to make the measurement easily and reliable, such as cup design, are presented. The instrument is used to monitor and analyze the elevation change of a 1000MW turbo-generator during the vacuum setup process. We find that the influence of vacuum on the elevation of bearing located on the exhaust cylinder is large. The maximum value is 1.8mm when vacuum changes from 0KPa to 90KPa. It causes unload of bearing #5~#8 and overload of bearing #2~#4. Adjustment project is given in the last of the paper to solve rub and pad fragment fault occurred in the unit. It is verified that the elevation adjustment for such kind of fault is valuable.